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Peremennye Zvezdy 26, No.4, 2006 Variable Stars 26, No.4, 2006 SAI, INASAN, Astronet.ru Moscow, Russia 2 June 2006 THE LIGHT CURVES OF TYPE Ia SUPERNOVA 2004fu 7 0 0 2 D. YU. TSVETKOV n 1 SternbergAstronomical Institute,University Ave.13, 119992 Moscow, Russia; e-mail: [email protected] a J Abstract 0 3 CCDUBVRI photometryispresentedfortypeIasupernova2004fu inNGC6949. Thelightand colour curves are typical for this class of objects, absolute magnitude at maximum and decline rate 2 are in agreement with therelationship between these parameters, established for SNeIa. v 1 5 0 SN 2004fu was discovered by Arbour (2004) on unfiltered CCD images taken with a 6 0 0.3-m Schmidt-Cassegrain reflector on November 4.87 (at mag approximately 16.8) and 6 5.81 (mag approximately 16.5). The new object was located at α = 20h35m11s.54,δ = 0 / +64◦48′25′′.7 (equinox 2000.0), which is 29′′ east and 15′′ north of the center of the Sc h p galaxy NGC 6949. - Modjazetal. (2004)reportthataspectrum(range350-740nm)ofSN2004fu,obtained o r on November 10.17 UT with the F. L. Whipple Observatory 1.5-m telescope, shows it to t s be a type-Ia supernova, several days before maximum light. a : v We started photometric observations of SN 2004fu immediately after discovery, on i X November 6, with 60-cm reflector of Crimean Observatory of Sternberg Astronomical r Institute (C60) equipped with Roper Scientific VersArray1300B CCD camera, and con- a tinued monitoring nearly each night until November 25. On November 22 images were obtained at 38-cm reflector of Crimean Astrophysical Observatory (C38) with Apogee AP-47p CCD camera. From 2004 December 29 until 2005 March 26 we observed SN 2004fu on four nights at 70-cm reflector in Moscow (M70) with AP-47p CCD camera, and on 2005 May 4 last images were obtained at C60. The reductions and photometric techniques were described by Tsvetkov (2006) and Tsvetkov et al. (2006). The image of SN 2004fu with comparison stars is shown in Fig. 1. Supernova is far away form the center of the galaxy and from the spiral arms, and the galaxy background does not affect the measurements. The magnitudes of the comparison stars are presented in Table 1, and photometry of SN is reported in Table 2. The light curves are shown in Fig. 2, where we also plotted the data obtained by amateur observers in the BVR bands reported at SNWeb.† Their data in B are in good agreement with our results, while in the V and R bands some systematic differences can be found. We achieved excellent photometric coverage on premaximum rise and first few days of brightness decline, but later only sporadic observations were obtained. We can derive dates and magnitudes of maximum light: Bmax = 15.87 on JD 2453326.3 †http://www.astrosurf.com/snweb2/2004/04fu/04fuMeas.htm PZ 26, 4(2006) 2 (November 16.8), Vmax = 15.42 on JD 2453327.2, Rmax = 15.18 on JD2453327.4. The date of maximum light in I is difficult to estimate with the same accuracy, as the light curve is quite flat near maximum, with Imax = 15.19. Using the data by amateurs, we can derive the decline rate parameter ∆m (B) = 1.3. We fitted the data with the light 15 curves of the well studied SN Ia 1994D (Richmond et al., 1995, Altavilla et al., 2004) with nearly the same value of ∆m (B). The agreement between the light curves of SN 2004fu 15 and 1994D is nearly perfect in the B and V bands near maximum, while in R and I some differences are evident. At late stages the difference between these objects is prominent in all bands except I, but the late light curves are not well sampled by our observations to allow definite conclusions. The colour curves for SN 2004fu are shown in Fig. 3 and are compared to those for SN 1994D. We see very good agreement between SN 2004fu and SN 1994D in (B − V) and some differences in (V −R). We shifted the (U −B),(B −V) and (V −R) colour curves of SN 1994D by 0.5, 0.41 and 0.25 mag, respectively. As the light of SN 1994D suffered negligible extinction both in the Galaxy and in the host galaxy (Altavilla et al., 2004), these values represent the total colour excess for SN 2004fu. Comparing these data with the estimates of galactic extinction from Schlegel et al. (1998) AU = 2.10,AB = 1.67,AV = 1.28,AR = 1.03 we conclude that all extinction towards SN 2004fu originated in the Galaxy. Taking these values for extinction and distance modulus µ=33.19 from the LEDA database, we derive absolute magnitudes at maximum light: MB = −18.99,MV = −19.05,MR = −19.04. These values are slightly fainter than average luminosity for SNe Ia and are in good agreement with the relationship between decline rate parameter and absolute magnitude for SNe Ia as presented by Phillips (2005) and Altavilla et al. (2004). We conclude that SN 2004fu is a typical object for its class regarding photometric behavior, with rate of decline after maximum slightly faster, and maximum luminosity lower than average, in accordance with the relationship between these parameters for SNe Ia. Acknowledgements: This research has made use of the Lyon-Meudon Extragalactic Database (LEDA). The author is grateful to I.M.Volkov for help in the observations. The work was partly supported by RFBR grant 05-02-17480. References: Altavilla, G., Fiorentino, G., Marconi, M., et al., 2004, MNRAS, 349, 1344 Arbour, R., 2004, IAU Circ., No. 8428 Modjaz, M., Challis, P., Kirshner, R., Westover, M., 2004, IAU Circ., No. 8436 Richmond, M.W., Treffers, R.R., Filippenko, A.V., et al., 1995, Astron. J., 109, 2121 Phillips, M.M.,2005,ASPConf. Ser.,342,211,in1604-2004: Supernovaeascosmological lighthouses, M.Turatto et al. eds. Schlegel, D., Finkbeiner, D., Davis, M., 1998, Astrophys. J., 500, 525 Tsvetkov, D.Yu., 2006, Permennye Zvezdy (Variable Stars), 23, No. 3 Tsvetkov, D.Yu., Volnova, A.A., Shulga, A.P., et al., 2006, Astron. & Astrophys. (sub- mitted), astro-ph/0605184 PZ 26, 4(2006) 3 Figure 1. SN 2004fu in NGC 6949 with comparison stars PZ 26, 4(2006) 4 Figure 2. BVRI light curves of SN 2004fu, showing our photometry (dots) and that of amateur observers (crosses). The dashed lines are the light curves of SN 1994D PZ 26, 4(2006) 5 Figure 3. (U −B),(B−V) and (V −R) colour curves of SN 2004fu. The dashed lines are the colour curves of SN 1994D PZ 26, 4(2006) 6 Table 1: Magnitudes of comparison stars Star U σU B σB V σV R σR I σI 1 14.66 0.06 14.59 0.03 13.85 0.04 13.34 0.02 12.92 0.02 2 16.00 0.04 15.25 0.04 13.96 0.03 13.19 0.03 12.55 0.02 3 15.73 0.07 15.25 0.04 14.22 0.04 13.59 0.03 13.12 0.02 Table 2: Photometry of SN 2004fu JD 2453000+ U σU B σB V σV R σR I σI Tel. 316.22 17.15 0.04 16.74 0.04 16.25 0.03 16.00 0.10 C60 317.19 16.84 0.04 16.50 0.04 16.01 0.03 15.75 0.04 C60 318.45 16.53 0.04 16.06 0.04 15.80 0.03 15.40 0.04 C60 319.35 16.35 0.04 15.97 0.04 15.62 0.03 15.36 0.04 C60 320.41 16.19 0.05 15.76 0.04 15.52 0.03 15.24 0.03 C60 323.47 16.07 0.12 15.92 0.06 15.57 0.05 15.30 0.04 15.20 0.04 C60 327.42 15.94 0.12 15.86 0.04 15.43 0.04 15.19 0.03 15.03 0.07 C60 329.15 16.04 0.05 15.90 0.04 15.45 0.04 15.22 0.03 15.23 0.03 C60 331.17 16.29 0.15 16.08 0.06 15.57 0.05 15.26 0.05 15.35 0.06 C60 332.15 16.10 0.06 15.57 0.05 15.28 0.05 15.41 0.05 C38 335.25 16.41 0.05 15.75 0.06 15.67 0.03 15.61 0.04 C60 369.22 17.65 0.08 17.05 0.09 M70 383.15 19.12 0.10 17.95 0.07 17.52 0.06 17.47 0.09 M70 406.21 19.00 0.17 18.44 0.12 18.42 0.19 M70 456.54 19.66 0.22 M70 495.49 21.20 0.30 C60